Anthropic: Claude Opus 4.7 (Fast) – API Quickstart

Sample code and API for Claude Opus 4.7 (Fast)

OpenRouter normalizes requests and responses across providers for you.

Get your API key

Create an API key from your OpenRouter dashboard and set it as an environment variable:

Make your first request

Use anthropic/claude-opus-4.7-fast with the OpenRouter API:

OpenRouter supports reasoning-enabled models that can show their step-by-step thinking process. Use the reasoning parameter in your request to enable reasoning, and access the reasoning_details array in the response to see the model's internal reasoning before the final answer. When continuing a conversation, preserve the complete reasoning_details when passing messages back to the model so it can continue reasoning from where it left off. Learn more about reasoning tokens.

In the examples below, the OpenRouter-specific headers are optional. Setting them allows your app to appear on the OpenRouter leaderboards.

Using third-party SDKs

For information about using third-party SDKs and frameworks with OpenRouter, please see our frameworks documentation.

Enable streaming

Add "stream": true to your request body to receive responses as server-sent events:

Endpoint

POSThttps://openrouter.ai/api/v1/chat/completions

AuthorizationBearer $OPENROUTER_API_KEY

Content-Typeapplication/json

HTTP-Refereroptional — your site URL, for rankings

X-Titleoptional — your site name, for rankings

Modelanthropic/claude-opus-4.7-fast

Parameters

Name	Type	Default	Description
`max_tokens`	integer	—	This sets the upper limit for the number of tokens the model can generate in response.
`stop`	array	—	Stop generation immediately if the model encounter any token specified in the stop array.
`reasoning`	map	—	Controls reasoning behavior for models that support thinking tokens, including whether reasoning is enabled, the reasoning effort, maximum reasoning tokens, and whether reasoning is excluded from the response.
`tool_choice`	string or object	—	Controls which (if any) tool is called by the model.
`tools`	array	—	Tool calling parameter, following OpenAI's tool calling request shape.
`response_format`	map	—	Forces the model to produce specific output format.
`verbosity`	enum	`medium`	Constrains the verbosity of the model's response.